Known radar systems which are currently used for distance measurement in vehicles essentially comprise two separate radars which operate in different frequency bands. For distance measurements in a near area (short range radar), radars which operate in a frequency band around a mid-frequency of 24 GHz are commonly used. In this case, the expression “near area” means distances in the range from 0 to about 20 meters from the vehicle (short range radar). The frequency band from 76 GHz to 77 GHz is currently used for distance measurements in the “far area”, that is for measurements in the range from about 20 meters to around 200 meters (long range radar). These different frequency bands are antithetical to the concept of one single radar system for both measurement areas and often require two separate radar devices.
The frequency band from 77 GHz to 81 GHz is likewise suitable for short range radar applications. A single multirange radar system which carries out distance measurements in the near area and far area using a single radio-frequency transmission module (RF front-end) has, however, not yet been feasible for various reasons. One reason is that circuits which are manufactured using III/V semiconductor technologies (for example gallium-arsenide technologies) are used at the moment to construct known radar systems. Gallium-arsenide technologies are admittedly highly suitable for the integration of radio-frequency components, but it is not possible to achieve a degree of integration which is as high, for example, of that which would be possible with silicon integration, as a result of technological restrictions. Furthermore, only a portion of the required electronics are manufactured using GaAs technology, so that a large number of different components are required to construct the overall system.
However, a high number of components is not desirable, since losses and reflections arise in each component, especially in the signal path downstream to the RF power amplifier. These losses and reflections have an undesired negative impact on the efficiency of the overall system. Thus there is a general need for a RF sender/receiver front-end which provides for high flexibility at high integration level and high efficiency.